The working principle of the mold return needle is mainly as follows:

1. The return needle device usually includes parts such as a needle body, a spring and a guide sleeve.

2. The rear end of the needle body is connected to a spring, and the front end is conical or spherical, which is used to eject the molded part.

3. A guide groove is set in the guide sleeve to keep the needle body aligned during movement.

4. When the mold is closed, the needle body is pushed back to compress the spring to store energy.

5. When the mold is opened, the spring releases energy and drives the needle body to move forward to eject the molded part.

6. By adjusting the spring preload and the shape of the needle tip, the ejection force of the return needle is controlled.

7. The high-precision guide mechanism ensures that the needle body movement is accurate and controllable.

8. The use of wear-resistant and anti-corrosion materials extends the service life.

9. The return needle device simplifies the demoulding process and improves the degree of automation of the mold.

In summary, the mold return needle uses the spring energy storage principle to realize automatic ejection of molded parts, which is one of the key components of mold automation.